Conventionally, containers have been used for eye drops including flexible container main bodies that house medicinal solutions and spouts that are provided on the container main bodies and for discharging the medicinal solutions housed therein.
In such a container, the medicinal solution is discharged from the spout when the container main body is pressed and deformed, so that the container main body reaches an internal pressure higher than the atmospheric pressure. Then, outside air is made to flow in from the spout of the container main body when the container main body is released from pressing, and the container main body reaches an internal pressure lower than the atmospheric pressure, so as to restore the container main body into the shape before pressing.
However, in such a container, normally, since pathogenic microorganisms such as fungi and viruses exist in outside air that flows into the container, there is a problem that the medicinal solution housed in the medicinal solution container is contaminated with such outside air.
Therefore, as a container for solving such a problem, known is a container including (1) a flexible container main body that houses a medicinal solution, (2) a discharge portion that is provided on the container main body and is for discharging the medicinal solution housed in the container main body when the container main body is pressed and deformed and the container main body reaches an internal pressure higher than the atmospheric pressure, (3) a check valve portion that is communicated with the exterior of the container main body and is for making outside air flow in the interior of the container main body when the container main body is released from pressing and the internal pressure of the container main body reaches a negative pressure. The check valve portion is designed for preventing the medicinal solution in the interior of the container main body from leaking when the internal pressure of the container main body reaches a positive pressure. And (4) a filter portion is provided at an upstream side further than the check valve portion in the flow-in direction of outside air in the container main body for purifying the outside air that flows in the check valve portion.
According to such a configuration, when the container main body is released from pressing and the container main body reaches an internal pressure lower than the atmospheric pressure, outside air passes through the filter portion, and is then made to flow in the interior of the container main body via the check valve. Therefore, since the outside air that flows in the container main body after releasing from pressing is purified by the filter portion, contamination of the medicinal solution housed in the container main body can be efficiently prevented.
Meanwhile, the spout of the container for eye drops according to the prior art has a function of a so-called pressure valve. The pressure valve is closed if a fluid pressure is not received from an upstream side in the discharge direction, and is opened to discharge a medicinal solution from the opening of the pressure valve when the fluid pressure is received from an upstream side in the discharge direction (Patent Documents 1 and 2 in the following). Due to this function, the opening of the pressure valve is blocked when the container main body is released from pressing and the container main body reaches an internal pressure lower than the atmospheric pressure, so that outside air and the medicinal solution remaining in the periphery of the opening of the pressure valve can be prevented from entering into the interior of the container main body.    Patent Document 1: Japanese Published Unexamined Patent Application No. JP2007-15739A    Patent Document 2: International Publication No. WO07/111256 Pamphlet    Patent Document 3: International Publication No. WO97/25253 Pamphlet    Patent Document 4: Publication of national Application No. JP2000-502978A (translation from Patent Document 3)